An investor buys 20-year bonds, each having semiannual coupons and each maturing at par. For each bond the purchase price produces the same yield rate. One bond has a par value of $500 and a coupon of $45. The other bond has a par value of $1000 and a coupon of $30. The dollar amount of premium on the first bond is twice as great as the dollar amount of discount on the second bond. Find the yield rate convertible semiannually.